Further description of the mechanism of allosteric regulation of alpha-isopropylmalate synthase, the first unique enzyme in leucine biosynthesis, in Salmonella typhimurium. Investigation of the significance of the association-dissociation equilibrium, in which this enzyme exists, for catalysis and feedback inhibition by leucine. Study of the possible involvement of alpha-isopropylmalate synthase in the repression of the leucine biosynthetic enzymes. Study of the evolution of the regulation of leucine biosynthesis by localizing and characterizing the enzymes of the leucine pathway in yeast.